1. Field of the Invention
This invention relates to a calcium borate overbased salicylate for use as an additive for petroleum products and more particularly to a calcium borate overbased salicylate having extremely fine meta-calcium borate particles with a particle diameter of not more than 200 angstrom are uniformly dispersed therein and exhibiting excellent performances as a multifunctional additive for petroleum products.
2. Prior Art
A boron compound serves to improve the oxidation stability, rust-preventing properties, friction reducing properties and extreme pressure properties of a lubricating oil. Further, it has recently been found that an alkaline earth borate has excellent acid neutralizing properties and excellent hydrolytic stability when compared with conventional calcium carbonate. Under such circumstances, many research workers have attempted to incorporate stably a boron compound in the form of an alkaline earth metal borate in a lubricating oil. Especially, processes for stabilizing an alkaline earth metal borate in the form of ultramicroparticles in an oil by using a metallic detergent, for example, an alkaline earth metal sulfonate or an alkaline earth metal salicylate as a protective colloid have been studied.
For example, U.S. Pat. No. 3,679,584 discloses a process comprising reacting an overbased alkaline earth metal carbonate, namely, an overbased alkaline earth metal sulfonate with boric acid and an alkaline earth metal hydroxide in a mineral oil or a diluent by heating lo while blowing carbon dioxide into the reaction system. Further, U.S. Pat. Nos. 3,829,381, 4,744,920, etc., disclose processes comprising reacting an overbased alkaline earth metal sulfonate with boric acid in a mineral oil. Furthermore. U.S. Pat. No. 4,539,126 discloses a process for reacting an alkaline earth metal carbonate overbased compound, namely, an overbased alkaline earth metal salicylate with boric acid in a diluent by heating.
According to these processes, the alkaline earth metal dispersions are prepared by the steps of reacting an alkaline earth metal carbonate dispersed in an overbased alkaline earth metal sulfonate or salicylate with boric acid which is a weak acid and then converting the surface of the thus obtained reaction product to an alkaline earth metal borate. Therefore, it is impossible in the conventional processes to obtain alkaline earth metal borate particles having such a uniform structure and small diameter as those obtained by directly reacting calcium hydroxide or oxide which is a strong base with orthoboric acid to prepare a calcium borate dispersion as in the present invention. In addition, the reaction ratio in the conventional processes will decrease because a part of the produced alkaline earth metal borate settles due to agglomeration of the dispersed particles during the reaction. Further, the alkaline earth metal dispersions prepared by these conventional methods are poor in various performances as an additive for petroleum products as compared with calcium borate overbased salicylate dispersions obtained by the present invention. On the other hand, the inventor of this invention disclosed in U.S. Pat. No. 4,539,126 (Japanese Patent Application Laid-Open No. 204298/1986) that an alkaline earth metal borate overbased sulfonate could be produced by reacting water with boric acid and an alkaline earth metal hydroxide or oxide by heating in an oil solution a neutral alkaline earth metal sulfonate, namely, by a one-stage reaction.
However, it turned out that the process disclosed in the Japanese Patent Laid-Open No. 204298/1986 could not provide any product of a high total base number, namely, a high-boron content product when it was applied to the production of an alkaline earth metal borate overbased salicylate, though it was suitable for the production of an alkaline earth metal borate overbased sulfonate.